Double Chooz Near Detector Guillaume MENTION CEA Saclay, DAPNIA/SPP Workshop AAP 2007 Friday, December 14 th,

Double Chooz detector capabilities - Double Chooz experiment - The site - The 2 identical detectors - The reactors: powerful anti-neutrino sources - Expected performance - Detection of reactor anti-neutrinos: e + and neutron - Anti-neutrino spectrum measurement (Far and Near detectors) - Thermal power measurement - Burn-up detection -Conclusions

Chooz power plant map Near site: D~380 m, overburden 120 mwe Far site: D~1.05 km, overburden 300 mwe TypePWR (N4) # Cores2 Th. Power8.5 GW th Operating since1996/1997 Load Factor78%

The experiment site ν ν ν ν ν ν ν ν 1051 m 380 m

Double Chooz: 2 phases Double Chooz phase 1: far detector only  may help to reach a higher precision on anti- e spectrum… Double Chooz phase 2: higher precision on anti- e spectrum ~ events in 3 years Timeline SiteProposalConstruction FarDesign Data Taking (Phase I) Cstr. Near Data Taking (Phase II)

Reactors are abundant antineutrino sources 235 U 239 Pu Days 235 U 239 Pu 238 U 241 Pu Fission percentages 235 U 239 Pu Energy released per fission MeV210.0 MeV Average energy of e 2.94 MeV2.84 MeV # e per fission > 1.8 MeV More than fissions/second

ν e identification: using coïncidences (allows strongly reducing backgrounds)‏ (1) 0,5 < E prompt < 10 MeV (2) 6 < E delayed < 10 MeV (3) 1 μs < Δt < 100 μs ― Σ ≃ 8 MeV E e+ + 1 MeV Δt < 100 μs t e+e+ n ν e Detection technique 50 years of Physics

Detector structure Far detector Double Chooz: 2 identical detectors Calibration Glove-Box Outer Veto: plastic scintillator panels -Target: 10.3 m 3 liquid scintillator doped with 0.1% of Gd  -Catcher : 22.6 m 3 liquid scintillator Buffer: 114 m 3 mineral oil with ~400 PMTs Inner Veto: 90 m 3 liquid scintillator with 80 PMTs Shielding: 15 cm steel 4 Liquid Volumes

9 Backgrounds fast neutrons Gd  ~ 8 MeV proton recoils μ → ( 9 Li, 8 He) → β- n γ PM + rocks + neutron-like event Accidentals ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Correlated (CHOOZ data)‏

Far detector capabilities Far site: phase I of Double Chooz Anti-neutrino spectrum measurement over 1.5 years. (~ anti-neutrinos): –Require the knowledge of the average power over 1.5 years –Require the knowledge of the average fuel composition over 1.5 years Would allow to measure the antineutrino rate at a statistical precision of 0.7% (in case of no systematics) But also the shape of the spectrum, with a statistical precision of 2 to 3% per energy bin (with 8 bins between 1.5 and 5.5 MeV). Systematical uncertainties reduce this potential which is limited by the knowledge on the detector normalization (~ 2%) and on the reactor powers (~ 2%). Backgrounds also lead to some systematical subtraction error around 1% per energy bin The measured spectrum will include the oscillation effect. E vis in MeV # anti- e in 1.5 years  stat  stat ”+”  syst

Map of the near site (Preliminary, still under study) Distance to reactor cores: 456 m & 340 m  385 m (1 R. with 2P th ) Neutrino fluxes: w/o eff. 496 anti- e /day  events in 3 years (all eff. included) Depth: 120 m.w.e. (  flux: ~ 3-4  /m -2 s -1 ) 456 m 340 m 160 m Chooz NPP, mass map Near site location Access tunnel

Huber & Schwetz hep-ph/ Thermal power measurement with the near detector 1  error on thermal power measurement ~ Double Chooz Near Thermal power is measured at ~2% (?) by the nuclear power companies Current measurement at reactor  3% but possibility of improvement What can only neutrino do: Independent method looking directly at the nuclear core, from outside Cross calibration of different power plants from different sites With Double Chooz Near Average power measurement of both reactors: 5-6% over 3 weeks Fig: Chooz cooling tubes = Assuming no knowledge on reactor (neither power nor fuel composition)

Following up the burn-up Days 235 U 239 Pu 238 U 241 Pu Fission percentages E vis in MeV # anti- e in 10 days Detector efficiency included. Average spectra (analytical estimations), no statistical fluctuations here Question: How far can we see two different burn-up? Try to answer with non-parametric statistical test: Kolmogorov-Smirnov

Days 235 U 239 Pu 238 U 241 Pu Fission percentages E vis in MeV # anti- e in 3 weeks events events Two extreme burn-up in 3 weeks (identical reactors) Preliminary 2 fixed fuel compositions (in fraction of fission per isotope) 235 U= Pu= U= Pu= U= Pu= U= Pu=0.08 Kolmogorov-Smirnov Test on Burn-up: Null hypothesisH 0 : the two “burn-up” induce identical anti- e spectra Shape only: P KS = 0.81 (Max Distance = )  Shapes are very close!!! Rate and shape: P KS = 1.3 x  Rates are very different (~7% diff. on # of anti- e )

E vis in MeV # anti- e in 10 days events events Two extreme Burn-up in 10 days (identical reactors) OR 16 days with R1 ON R2 OFF OR 29 days with R1 OFF R2 ON Days 235 U 239 Pu 238 U 241 Pu Fission percentages Preliminary 2 fixed fuel compositions (in fraction of fission per isotope) 235 U= Pu= U= Pu= U= Pu= U= Pu=0.08 Kolmogorov-Smirnov Test on Burn-up: Null hypothesisH 0 : the two “burn-up” induce identical anti- e spectra Shape only: P KS = 0.99 (Max Distance = )  Shapes look identical!!! Rate and shape: P KS = 1.8 x  Rates are different (~7% diff. on # of anti- e )

E vis in MeV # anti- e in 3 weeks events events Two closer burn-up in 3 weeks (identical reactors) Days 235 U 239 Pu 238 U 241 Pu Fission percentages Preliminary 2 fixed fuel compositions (in fraction of fission per isotope) 235 U= Pu= U= Pu= U= Pu= U= Pu=0.06 Kolmogorov-Smirnov Test on Burn-up: Null hypothesisH 0 : the two “burn-up” induce identical anti- e spectra Shape only: P KS = (Max Distance = 0.006)  Shapes look identical!!! Rate and shape: P KS =  Rates are different (~4 % diff. on # of anti- e )

E vis in MeV # anti- e in 3 weeks events events Two still closer burn-up in 3 weeks (identical reactors) Days 235 U 239 Pu 238 U 241 Pu Fission percentages Preliminary 2 fixed fuel compositions (in fraction of fission per isotope) 235 U= Pu= U= Pu= U= Pu= U= Pu=0.03 Kolmogorov-Smirnov Test on Burn-up: Null hypothesisH 0 : the two “burn-up” induce identical anti- e spectra Shape only: P KS = 1.00 (Max Distance = 0.002)  Looks identical!!! Rate and shape: P KS = 0.55  Rates are too close, spectra match (~2 % diff. on # of anti- e )

Conclusion & Outlook - Neutrinos could “take a picture” of the nuclear cores  Thermal power measurement & non proliferation applications - Thermal power measurement will rely on the absolute normalization (but time-relative measurement of interest for burn-up, cross calibration) - Non proliferation applications will rely on time-relative measurements (try to detect an ‘abnormal’ burn-up) - Double Chooz Near detector will provide an unrivalled anti- e spectrum measurement. These data will be an incredibly rich source of information in order to look for power, burn-up correlations with anti- e spectra as a first step toward isotopic core composition. - However more precise determination of reactor power and some hints of isotopic composition might be obtained only with a closer detector to a single reactor.

Thank you for your attention! It’s time for lunch now!

Systematics ( Total ~0.45% without contingency ….) (see next slide)‏ Measured with several methods ‘’identical’’ Target geometry & LS Same scintillator batch + Stability Accurate T control (near/far)‏ Same weight sensor for both det. Distance 10 cm + monitor core barycenter Two ‘’identical’’ detectors, Low bkg < 0.6 %2.7 %Total %1.5 %From 7 to 3 cutsAnalysis <0.1 %1.0 %Spatial effects <0.2%1.2 % H/C ratio & Gd concentration <0.1 %0.3 %Density <0.1 %0.3 %Solid angle 0.25 %few %Live time 0.2 %0.3 %Target Mass Detector - induced <0.1 %0.6 %Energy per fission <0.1 %0.7 %Reactor power <0.1 %1.9 % flux and  Reactor- induced Double Chooz (relative)‏Chooz